(1) Field of the Invention
The present invention relates to a process for preparing 2'-deoxy-5-trifluoromethyl-.beta.-uridine which is useful per se as a carcinostatic agent and is a raw material of other pharmaceutically useful compounds.
(2) Description of the Related Arts
2'-deoxy-5-trifluoromethyl-.beta.-uridine is useful per se as a carcinostatic agent and is a raw material of other pharmaceutically useful compounds, and thus the demand thereof is increasing.
In the conventional process for preparing 2'-deoxy-5-trifluoromethyl-.beta.-uridine, there are known the following methods:
(a) a method for transforming the nucleic base from thymidine and 5-trifluoromethyluracil with an enzyme such as nucleoside-2'-deoxyribose transferase [Methods Carbohydr. Chem., 7, 19 (1976)]; PA0 (b) a method as a chemical synthesis of preparing an anomeric mixture by the condensation of a 5-trifluoromethylurasil derivative and a 2-deoxy-D-erythro-pentofuranose derivative in the presence of a catalyst and isolating the .beta.-isomer as the aimed product [J. Org. Chem., 31, 1181 (1966); U.S. Pat. No. 3531464]; and PA0 (c) a method of halogenating the 5-position of 2'-deoxy-.beta.-uridine as a raw material and then subjecting the halogenated product to trifluoromethylation [J. Chem. Soc. Perkin Trans. I, 2755, 1980].
However, the aforementioned production methods have the following defects:
The production method (a) is not suited for a large scale production because of the problems of the isolation of the aimed product or the productivity; a harmful mercury salt is used and complicated and tedious operations are needed for isolating the .beta.-isomer as the aimed product from the anomeric mixture in the production method (b); and 2'-deoxy-.beta.-uridine as a raw material is expensive in the production method (c).
Thus, none of the methods (a)-(c) is suitable for the industrial production method.
Therefore, a process for preparing 2'-deoxy-5-trifluoromethyl-.beta.-uridine suitable for industrial production has been desired in which the aforementioned problems in the conventional methods have been solved and a large amount of the product can be easily supplied.